Electric-only and hybrid electric vehicles have become increasingly capable and increasingly popular in recent years, as rising fossil fuel prices and improved battery technologies level the cost and performance fields between the vehicle types. Indeed, while the range and acceleration of production-level electric vehicles have historically lagged behind those of their fuel-powered counterparts, this situation is rapidly changing as high-capacity battery technologies are optimized and commercialized.
Nonetheless, despite the increasing parity between electric vehicles and fuel-powered vehicles, there are numerous differences between the vehicle types that require different handling and operational procedures. For example, the voltage present in a fuel-powered vehicle is generally fairly low, e.g., 12 volts, with the exception of certain sheltered areas such as spark plugs and ignition-related capacitors and transformers. In contrast, the core power system in an electric vehicle often exposes very high voltages, e.g., hundreds of volts, and does so at significant current levels.
Moreover, the charging and discharging of high-capacity electrical cells require more care than the analogous activity of filling a gas tank and using the gas. For example, many battery technologies require that the discharge cycle be controlled such that the battery cells are not discharged to a state of less than a certain voltage value per cell. Discharge rates are also often limited. Thus, it is important to control the rate at which battery cells are discharged and to monitor and cease the discharge before it reaches a level that may damage one or more cells of the battery.
One way to prevent a battery or battery bank from overly discharging or from exposing a dangerous voltage level at an inappropriate time is to use one or more contactors to isolate the battery from the remaining components and circuitry of the vehicle. This is also useful as an interlock feature, so that if a motor controller were to malfunction and present a short-circuit, the contactors can disconnect power and prevent an undesired acceleration.
However, while the use of contactors is generally beneficial, the inventors have discovered that there are situations wherein the contactors can also cause inconvenience for the operator or service personnel. It is an object in certain implementations of the invention to provide a system that may prevent or overcome certain of these problems. Nonetheless, it will be appreciated that the invention is not limited to systems that solve the problems noted herein. Moreover, the inventors have created the above body of information for the convenience of the reader and expressly disclaim all of the foregoing as prior art; the foregoing is a discussion of problems discovered and/or appreciated by the inventors, and is not an attempt to review or catalog the prior art.